/// MO is an operand of SU's instruction that defines a physical register. Add
/// data dependencies from SU to any uses of the physical register.
void ScheduleDAGInstrs::addPhysRegDataDeps(SUnit *SU, unsigned OperIdx) {
const MachineOperand &MO = SU->getInstr()->getOperand(OperIdx);
assert(MO.isDef() && "expect physreg def");
// Ask the target if address-backscheduling is desirable, and if so how much.
const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
unsigned SpecialAddressLatency = ST.getSpecialAddressLatency();
unsigned DataLatency = SU->Latency;
for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
Alias.isValid(); ++Alias) {
if (!Uses.contains(*Alias))
continue;
std::vector<PhysRegSUOper> &UseList = Uses[*Alias];
for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
SUnit *UseSU = UseList[i].SU;
if (UseSU == SU)
continue;
MachineInstr *UseMI = UseSU->getInstr();
int UseOp = UseList[i].OpIdx;
unsigned LDataLatency = DataLatency;
// Optionally add in a special extra latency for nodes that
// feed addresses.
// TODO: Perhaps we should get rid of
// SpecialAddressLatency and just move this into
// adjustSchedDependency for the targets that care about it.
if (SpecialAddressLatency != 0 && !UnitLatencies &&
UseSU != &ExitSU) {
const MCInstrDesc &UseMCID = UseMI->getDesc();
int RegUseIndex = UseMI->findRegisterUseOperandIdx(*Alias);
assert(RegUseIndex >= 0 && "UseMI doesn't use register!");
if (RegUseIndex >= 0 &&
(UseMI->mayLoad() || UseMI->mayStore()) &&
(unsigned)RegUseIndex < UseMCID.getNumOperands() &&
UseMCID.OpInfo[RegUseIndex].isLookupPtrRegClass())
LDataLatency += SpecialAddressLatency;
}
// Adjust the dependence latency using operand def/use
// information (if any), and then allow the target to
// perform its own adjustments.
SDep dep(SU, SDep::Data, LDataLatency, *Alias);
if (!UnitLatencies) {
unsigned Latency =
TII->computeOperandLatency(InstrItins, SU->getInstr(), OperIdx,
(UseOp < 0 ? 0 : UseMI), UseOp);
dep.setLatency(Latency);
unsigned MinLatency =
TII->computeOperandLatency(InstrItins, SU->getInstr(), OperIdx,
(UseOp < 0 ? 0 : UseMI), UseOp,
/*FindMin=*/true);
dep.setMinLatency(MinLatency);
ST.adjustSchedDependency(SU, UseSU, dep);
}
UseSU->addPred(dep);
}
}
}
/// MO is an operand of SU's instruction that defines a physical register. Add
/// data dependencies from SU to any uses of the physical register.
void ScheduleDAGInstrs::addPhysRegDataDeps(SUnit *SU,
const MachineOperand &MO) {
assert(MO.isDef() && "expect physreg def");
// Ask the target if address-backscheduling is desirable, and if so how much.
const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
unsigned SpecialAddressLatency = ST.getSpecialAddressLatency();
unsigned DataLatency = SU->Latency;
for (const unsigned *Alias = TRI->getOverlaps(MO.getReg()); *Alias; ++Alias) {
if (!Uses.contains(*Alias))
continue;
std::vector<SUnit*> &UseList = Uses[*Alias];
for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
SUnit *UseSU = UseList[i];
if (UseSU == SU)
continue;
unsigned LDataLatency = DataLatency;
// Optionally add in a special extra latency for nodes that
// feed addresses.
// TODO: Perhaps we should get rid of
// SpecialAddressLatency and just move this into
// adjustSchedDependency for the targets that care about it.
if (SpecialAddressLatency != 0 && !UnitLatencies &&
UseSU != &ExitSU) {
MachineInstr *UseMI = UseSU->getInstr();
const MCInstrDesc &UseMCID = UseMI->getDesc();
int RegUseIndex = UseMI->findRegisterUseOperandIdx(*Alias);
assert(RegUseIndex >= 0 && "UseMI doesn't use register!");
if (RegUseIndex >= 0 &&
(UseMI->mayLoad() || UseMI->mayStore()) &&
(unsigned)RegUseIndex < UseMCID.getNumOperands() &&
UseMCID.OpInfo[RegUseIndex].isLookupPtrRegClass())
LDataLatency += SpecialAddressLatency;
}
// Adjust the dependence latency using operand def/use
// information (if any), and then allow the target to
// perform its own adjustments.
const SDep& dep = SDep(SU, SDep::Data, LDataLatency, *Alias);
if (!UnitLatencies) {
ComputeOperandLatency(SU, UseSU, const_cast<SDep &>(dep));
ST.adjustSchedDependency(SU, UseSU, const_cast<SDep &>(dep));
}
UseSU->addPred(dep);
}
}
}
void ScheduleDAGInstrs::BuildSchedGraph(AliasAnalysis *AA) {
// We'll be allocating one SUnit for each instruction, plus one for
// the region exit node.
SUnits.reserve(BB->size());
// We build scheduling units by walking a block's instruction list from bottom
// to top.
// Remember where a generic side-effecting instruction is as we procede.
SUnit *BarrierChain = 0, *AliasChain = 0;
// Memory references to specific known memory locations are tracked
// so that they can be given more precise dependencies. We track
// separately the known memory locations that may alias and those
// that are known not to alias
std::map<const Value *, SUnit *> AliasMemDefs, NonAliasMemDefs;
std::map<const Value *, std::vector<SUnit *> > AliasMemUses, NonAliasMemUses;
// Keep track of dangling debug references to registers.
std::vector<std::pair<MachineInstr*, unsigned> >
DanglingDebugValue(TRI->getNumRegs(),
std::make_pair(static_cast<MachineInstr*>(0), 0));
// Check to see if the scheduler cares about latencies.
bool UnitLatencies = ForceUnitLatencies();
// Ask the target if address-backscheduling is desirable, and if so how much.
const TargetSubtarget &ST = TM.getSubtarget<TargetSubtarget>();
unsigned SpecialAddressLatency = ST.getSpecialAddressLatency();
// Remove any stale debug info; sometimes BuildSchedGraph is called again
// without emitting the info from the previous call.
DbgValueVec.clear();
// Model data dependencies between instructions being scheduled and the
// ExitSU.
AddSchedBarrierDeps();
// Walk the list of instructions, from bottom moving up.
for (MachineBasicBlock::iterator MII = InsertPos, MIE = Begin;
MII != MIE; --MII) {
MachineInstr *MI = prior(MII);
// DBG_VALUE does not have SUnit's built, so just remember these for later
// reinsertion.
if (MI->isDebugValue()) {
if (MI->getNumOperands()==3 && MI->getOperand(0).isReg() &&
MI->getOperand(0).getReg())
DanglingDebugValue[MI->getOperand(0).getReg()] =
std::make_pair(MI, DbgValueVec.size());
DbgValueVec.push_back(MI);
continue;
}
const TargetInstrDesc &TID = MI->getDesc();
assert(!TID.isTerminator() && !MI->isLabel() &&
"Cannot schedule terminators or labels!");
// Create the SUnit for this MI.
SUnit *SU = NewSUnit(MI);
SU->isCall = TID.isCall();
SU->isCommutable = TID.isCommutable();
// Assign the Latency field of SU using target-provided information.
if (UnitLatencies)
SU->Latency = 1;
else
ComputeLatency(SU);
// Add register-based dependencies (data, anti, and output).
for (unsigned j = 0, n = MI->getNumOperands(); j != n; ++j) {
const MachineOperand &MO = MI->getOperand(j);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
assert(TRI->isPhysicalRegister(Reg) && "Virtual register encountered!");
if (MO.isDef() && DanglingDebugValue[Reg].first!=0) {
SU->DbgInstrList.push_back(DanglingDebugValue[Reg].first);
DbgValueVec[DanglingDebugValue[Reg].second] = 0;
DanglingDebugValue[Reg] = std::make_pair((MachineInstr*)0, 0);
}
std::vector<SUnit *> &UseList = Uses[Reg];
std::vector<SUnit *> &DefList = Defs[Reg];
// Optionally add output and anti dependencies. For anti
// dependencies we use a latency of 0 because for a multi-issue
// target we want to allow the defining instruction to issue
// in the same cycle as the using instruction.
// TODO: Using a latency of 1 here for output dependencies assumes
// there's no cost for reusing registers.
SDep::Kind Kind = MO.isUse() ? SDep::Anti : SDep::Output;
unsigned AOLatency = (Kind == SDep::Anti) ? 0 : 1;
for (unsigned i = 0, e = DefList.size(); i != e; ++i) {
SUnit *DefSU = DefList[i];
if (DefSU == &ExitSU)
continue;
if (DefSU != SU &&
(Kind != SDep::Output || !MO.isDead() ||
!DefSU->getInstr()->registerDefIsDead(Reg)))
DefSU->addPred(SDep(SU, Kind, AOLatency, /*Reg=*/Reg));
}
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
std::vector<SUnit *> &DefList = Defs[*Alias];
for (unsigned i = 0, e = DefList.size(); i != e; ++i) {
SUnit *DefSU = DefList[i];
if (DefSU == &ExitSU)
continue;
if (DefSU != SU &&
(Kind != SDep::Output || !MO.isDead() ||
!DefSU->getInstr()->registerDefIsDead(*Alias)))
DefSU->addPred(SDep(SU, Kind, AOLatency, /*Reg=*/ *Alias));
}
}
if (MO.isDef()) {
// Add any data dependencies.
unsigned DataLatency = SU->Latency;
for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
SUnit *UseSU = UseList[i];
if (UseSU == SU)
continue;
unsigned LDataLatency = DataLatency;
// Optionally add in a special extra latency for nodes that
// feed addresses.
// TODO: Do this for register aliases too.
// TODO: Perhaps we should get rid of
// SpecialAddressLatency and just move this into
// adjustSchedDependency for the targets that care about it.
if (SpecialAddressLatency != 0 && !UnitLatencies &&
UseSU != &ExitSU) {
MachineInstr *UseMI = UseSU->getInstr();
const TargetInstrDesc &UseTID = UseMI->getDesc();
int RegUseIndex = UseMI->findRegisterUseOperandIdx(Reg);
assert(RegUseIndex >= 0 && "UseMI doesn's use register!");
if (RegUseIndex >= 0 &&
(UseTID.mayLoad() || UseTID.mayStore()) &&
(unsigned)RegUseIndex < UseTID.getNumOperands() &&
UseTID.OpInfo[RegUseIndex].isLookupPtrRegClass())
LDataLatency += SpecialAddressLatency;
}
// Adjust the dependence latency using operand def/use
// information (if any), and then allow the target to
// perform its own adjustments.
const SDep& dep = SDep(SU, SDep::Data, LDataLatency, Reg);
if (!UnitLatencies) {
ComputeOperandLatency(SU, UseSU, const_cast<SDep &>(dep));
ST.adjustSchedDependency(SU, UseSU, const_cast<SDep &>(dep));
}
UseSU->addPred(dep);
}
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
std::vector<SUnit *> &UseList = Uses[*Alias];
for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
SUnit *UseSU = UseList[i];
if (UseSU == SU)
continue;
const SDep& dep = SDep(SU, SDep::Data, DataLatency, *Alias);
if (!UnitLatencies) {
ComputeOperandLatency(SU, UseSU, const_cast<SDep &>(dep));
ST.adjustSchedDependency(SU, UseSU, const_cast<SDep &>(dep));
}
UseSU->addPred(dep);
}
}
// If a def is going to wrap back around to the top of the loop,
// backschedule it.
if (!UnitLatencies && DefList.empty()) {
LoopDependencies::LoopDeps::iterator I = LoopRegs.Deps.find(Reg);
if (I != LoopRegs.Deps.end()) {
const MachineOperand *UseMO = I->second.first;
unsigned Count = I->second.second;
const MachineInstr *UseMI = UseMO->getParent();
unsigned UseMOIdx = UseMO - &UseMI->getOperand(0);
const TargetInstrDesc &UseTID = UseMI->getDesc();
// TODO: If we knew the total depth of the region here, we could
// handle the case where the whole loop is inside the region but
// is large enough that the isScheduleHigh trick isn't needed.
if (UseMOIdx < UseTID.getNumOperands()) {
// Currently, we only support scheduling regions consisting of
// single basic blocks. Check to see if the instruction is in
// the same region by checking to see if it has the same parent.
if (UseMI->getParent() != MI->getParent()) {
unsigned Latency = SU->Latency;
if (UseTID.OpInfo[UseMOIdx].isLookupPtrRegClass())
Latency += SpecialAddressLatency;
// This is a wild guess as to the portion of the latency which
// will be overlapped by work done outside the current
// scheduling region.
Latency -= std::min(Latency, Count);
// Add the artificial edge.
ExitSU.addPred(SDep(SU, SDep::Order, Latency,
/*Reg=*/0, /*isNormalMemory=*/false,
/*isMustAlias=*/false,
/*isArtificial=*/true));
} else if (SpecialAddressLatency > 0 &&
UseTID.OpInfo[UseMOIdx].isLookupPtrRegClass()) {
// The entire loop body is within the current scheduling region
// and the latency of this operation is assumed to be greater
// than the latency of the loop.
// TODO: Recursively mark data-edge predecessors as
// isScheduleHigh too.
SU->isScheduleHigh = true;
}
}
LoopRegs.Deps.erase(I);
}
}
UseList.clear();
if (!MO.isDead())
DefList.clear();
DefList.push_back(SU);
} else {
UseList.push_back(SU);
}
}
// Add chain dependencies.
// Chain dependencies used to enforce memory order should have
// latency of 0 (except for true dependency of Store followed by
// aliased Load... we estimate that with a single cycle of latency
// assuming the hardware will bypass)
// Note that isStoreToStackSlot and isLoadFromStackSLot are not usable
// after stack slots are lowered to actual addresses.
// TODO: Use an AliasAnalysis and do real alias-analysis queries, and
// produce more precise dependence information.
#define STORE_LOAD_LATENCY 1
unsigned TrueMemOrderLatency = 0;
if (TID.isCall() || MI->hasUnmodeledSideEffects() ||
(MI->hasVolatileMemoryRef() &&
(!TID.mayLoad() || !MI->isInvariantLoad(AA)))) {
// Be conservative with these and add dependencies on all memory
// references, even those that are known to not alias.
for (std::map<const Value *, SUnit *>::iterator I =
NonAliasMemDefs.begin(), E = NonAliasMemDefs.end(); I != E; ++I) {
I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
}
for (std::map<const Value *, std::vector<SUnit *> >::iterator I =
NonAliasMemUses.begin(), E = NonAliasMemUses.end(); I != E; ++I) {
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
I->second[i]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
}
NonAliasMemDefs.clear();
NonAliasMemUses.clear();
// Add SU to the barrier chain.
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
BarrierChain = SU;
// fall-through
new_alias_chain:
// Chain all possibly aliasing memory references though SU.
if (AliasChain)
AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
AliasChain = SU;
for (unsigned k = 0, m = PendingLoads.size(); k != m; ++k)
PendingLoads[k]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
for (std::map<const Value *, SUnit *>::iterator I = AliasMemDefs.begin(),
E = AliasMemDefs.end(); I != E; ++I) {
I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
}
for (std::map<const Value *, std::vector<SUnit *> >::iterator I =
AliasMemUses.begin(), E = AliasMemUses.end(); I != E; ++I) {
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
I->second[i]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
}
PendingLoads.clear();
AliasMemDefs.clear();
AliasMemUses.clear();
} else if (TID.mayStore()) {
bool MayAlias = true;
TrueMemOrderLatency = STORE_LOAD_LATENCY;
if (const Value *V = getUnderlyingObjectForInstr(MI, MFI, MayAlias)) {
// A store to a specific PseudoSourceValue. Add precise dependencies.
// Record the def in MemDefs, first adding a dep if there is
// an existing def.
std::map<const Value *, SUnit *>::iterator I =
((MayAlias) ? AliasMemDefs.find(V) : NonAliasMemDefs.find(V));
std::map<const Value *, SUnit *>::iterator IE =
((MayAlias) ? AliasMemDefs.end() : NonAliasMemDefs.end());
if (I != IE) {
I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0, /*Reg=*/0,
/*isNormalMemory=*/true));
I->second = SU;
} else {
if (MayAlias)
AliasMemDefs[V] = SU;
else
NonAliasMemDefs[V] = SU;
}
// Handle the uses in MemUses, if there are any.
std::map<const Value *, std::vector<SUnit *> >::iterator J =
((MayAlias) ? AliasMemUses.find(V) : NonAliasMemUses.find(V));
std::map<const Value *, std::vector<SUnit *> >::iterator JE =
((MayAlias) ? AliasMemUses.end() : NonAliasMemUses.end());
if (J != JE) {
for (unsigned i = 0, e = J->second.size(); i != e; ++i)
J->second[i]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency,
/*Reg=*/0, /*isNormalMemory=*/true));
J->second.clear();
}
if (MayAlias) {
// Add dependencies from all the PendingLoads, i.e. loads
// with no underlying object.
for (unsigned k = 0, m = PendingLoads.size(); k != m; ++k)
PendingLoads[k]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
// Add dependence on alias chain, if needed.
if (AliasChain)
AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
}
// Add dependence on barrier chain, if needed.
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
} else {
// Treat all other stores conservatively.
goto new_alias_chain;
}
if (!ExitSU.isPred(SU))
// Push store's up a bit to avoid them getting in between cmp
// and branches.
ExitSU.addPred(SDep(SU, SDep::Order, 0,
/*Reg=*/0, /*isNormalMemory=*/false,
/*isMustAlias=*/false,
/*isArtificial=*/true));
} else if (TID.mayLoad()) {
bool MayAlias = true;
TrueMemOrderLatency = 0;
if (MI->isInvariantLoad(AA)) {
// Invariant load, no chain dependencies needed!
} else {
if (const Value *V =
getUnderlyingObjectForInstr(MI, MFI, MayAlias)) {
// A load from a specific PseudoSourceValue. Add precise dependencies.
std::map<const Value *, SUnit *>::iterator I =
((MayAlias) ? AliasMemDefs.find(V) : NonAliasMemDefs.find(V));
std::map<const Value *, SUnit *>::iterator IE =
((MayAlias) ? AliasMemDefs.end() : NonAliasMemDefs.end());
if (I != IE)
I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0, /*Reg=*/0,
/*isNormalMemory=*/true));
if (MayAlias)
AliasMemUses[V].push_back(SU);
else
NonAliasMemUses[V].push_back(SU);
} else {
// A load with no underlying object. Depend on all
// potentially aliasing stores.
for (std::map<const Value *, SUnit *>::iterator I =
AliasMemDefs.begin(), E = AliasMemDefs.end(); I != E; ++I)
I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
PendingLoads.push_back(SU);
MayAlias = true;
}
// Add dependencies on alias and barrier chains, if needed.
if (MayAlias && AliasChain)
AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
}
}
}
for (int i = 0, e = TRI->getNumRegs(); i != e; ++i) {
Defs[i].clear();
Uses[i].clear();
}
PendingLoads.clear();
}
